1. Field of the Invention
The present invention relates to a method and apparatus for testing the integrity of filter elements in a filter assembly. The invention is particularly applicable to filter systems comprising a very large number of filter elements where the determination of a defective element among so many elements becomes difficult.
2. Description of the Related Art
Large dimensioned filter systems of various construction are known in which 100 or more filter elements are arranged in one large filter housing. In many applications, for example, in the food and beverage industry or in the pharmaceutical industry, large scale filtration also has to be carried out under sterile conditions. Not only the filter housing but the filter elements along with the filter material must be regularly sterilized. Such sterilization performed for example with hot water or steam can deteriorate the integrity of the filter material, especially when as the sterilization has to be carried out frequently.
Deterioration of the filter material and/or other parts of the filter element can also arise in other applications, for example, when chemically aggressive substances or high temperature gases are to be filtered. The deterioration of the filter element can occur in the form of the filter material itself being degraded or a joining of the filter material to the filter housing may become defective and act as a by-pass, i.e. furnish an opening greater than the pore size of the filter material.
In actual practice, the filter elements are often built into filtration systems which are an integral part of some production operations. It would be a considerable drawback if the operation had to be shut down and the filtration system had to be dismantled to inspect the filter integrity at given service intervals. A fast and convenient method is needed of in situ testing in built-in systems, which requires little down time of the filtration operation.
In large filter systems, just one or more defective filter elements can lead to a substantial bacteria contamination of the filtered fluid and possibly the shut-down of the filtration operation. Finding the particular element or elements responsible among the 100 or more elements can be a very time-consuming task, particularly if this is done on a trial and error basis. Means of locating the defective elements in a systematic way are needed.